Nonphotosynthetic organisms

The path from squalene (114) to the corresponding oxide and thence to lanosterol [79-63-0] (126), C qH qO, cholesterol [57-88-5] (127), and cycloartenol [469-38-5] (128) (Fig. 6) has been demonstrated in nonphotosynthetic organisms. It has not yet been demonstrated that there is an obligatory path paralleling the one known for generation of plant sterols despite the obvious stmctural relationships of, for example, cycloartenol (128), C qH qO, to cyclobuxine-D (129), C25H42N2O. The latter, obtained from the leaves of Buxus sempervirens E., has apparentiy found use medicinally for many disorders, from skin and venereal diseases to treatment of malaria and tuberculosis. In addition to cyclobuxine-D [2241-90-9] (129) from the Buxaceae, steroidal alkaloids are also found in the Solanaceae, Apocynaceae, and LiUaceae. 

Carotenoid distribution in fungi, nonphotosynthetic organisms, are apparently capricious, but they usually accumulate carotenes, mono- and bicyclic carotenoids, and lack carotenoids with e rings. Plectaniaxanthin in Ascomycetes and canthaxan-thin in Canthardlus cinnabarinus have been found. ... 

Because mankind, like other nonphotosynthetic organisms, developed survival strategies based on the exploitation of photosynthetic plants, there are many traditional uses for biopolymers that are unlikely to be replaced in a foreseeable future. The largest use of cultivated plants is as human food, as animal feed, and in fiber production, with a relatively tiny acreage devoted to specialty crops for spices, herbs, drugs, and textile fibers (77). 

The transfer of phosphoryl groups is a central feature of metabolism. Equally important is another kind of transfer, electron transfer in oxidation-reduction reactions. These reactions involve the loss of electrons by one chemical species, which is thereby oxidized, and the gain of electrons by another, which is reduced. The flow of electrons in oxidation-reduction reactions is responsible, directly or indirectly, for all work done by living organisms. In nonphotosynthetic organisms, the sources of electrons are reduced compounds (foods) in photosynthetic organisms, the initial electron donor is a chemical species excited by the absorption of light. The path of electron flow in metabolism is complex. Electrons move from various metabolic intermediates to specialized electron carriers in enzyme-catalyzed reactions. 

Plant mitochondria supply the cell with ATP during periods of low illumination or darkness by mechanisms entirely analogous to those used by nonphotosynthetic organisms. In the light, the principal source of mitochondrial NADH is a reaction in which glycine, produced by a process known as photorespiration, is converted to serine (see Fig. 20-21) ... 

A small number of other biosynthetic pathways, which are used by both photosynthetic and nonphotosynthetic organisms, are indicated in Fig. 10-1. For example, pyruvate is converted readily to the amino acid t-alanine and oxaloacetate to L-aspartic acid the latter, in turn, may be utilized in the biosynthesis of pyrimidines. Other amino acids, purines, and additional compounds needed for construction of cells are formed in pathways, most of which branch from some compound shown in Fig. 10-1 or from a point on one of the pathways shown in the figure. In virtually every instance biosynthesis is dependent upon a supply of energy furnished by the cleavage to ATP. In many cases it also requires one of the hydrogen carriers in a reduced form. While Fig. 10-1 outlines in briefest form a minute fraction of the metabolic pathways known, the ones shown are of central importance. 

Recall that the original development of eukaryotic creatures may have started with a symbiotic relationship between two prokaryotes and that symbiosis between algae and nonphotosynthetic organisms may have led to development of higher plants. Associations between species are still important today. For example, the bacteria in the protozoa of the digestive tract of ruminant animals are essential to production of meat. Our own bodies play host to bacteria, fungi,... 

It is interesting to note that the UV spectrum for the ferredoxin from chromatium, a photosynthesizing bacteria, suggests that it is very similar, if not identical, to that of the ferredoxin from clostridia, which are nonphotosynthetic organisms. It was originally suggested that this is a form of ferredoxin intermediate between the plant type and the clostridial type, because chemical analysis suggested that the iron content was intermediate between the chloroplast and clostridial type ferredoxin. 

In bacterially regulated (nonilluminated, nonphotosynthetic) organic sediments, rates of bacterial metabolism and oxygen consumption increased with increasing temperatures, particularly above 17°C (Kamp-Nielsen, 1975). Above this temperature, release of phosphorus to the overlying... 

The basic tenets of assimilatory sulfate reduction were first elucidated in yeast (see review by Wilson, 1962). A recent reinvestigation of the pathway has confirmed that PAPS serves as the substrate for reduction in this organism (Wilson and Bierer, 1976) and several other nonphotosynthetic organisms (Tsang and Schiflf, 1975, 1976a). For some years it was assumed that PAPS also served as the substrate for reduction in plants and some evidence has been advanced in support of this proposal (Burnell and Anderson, 1973a Hodson et al, 1968 Schwenn and Hennies, 1974). 

Anabaena T-1 and spinach chloroplast Tm are the most abundant thioredoxins in vivo. They exhibit approximately 50% sequence homology to thioredoxins from other nonphotosynthetic organisms (9). They can be reduced by NADPH and the flavoprotein-type reductase (10). Presumably they have intracellular functions which are common to thioredoxins in all living organisms, such as deoxynucleotide synthesis and sulfate metabolism. 

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